As aromatic polysulfone resin has excellent heat resistance and chemical resistance, it is used in a variety of applications. One such application is as material of porous membranes used in filtration such as ultrafiltration and microfiltration. For example, JP-2006-230459-A (Patent Document 1) describes use of aromatic polysulfone resin as material of porous hollow-fiber membrane, and specifically presents an example of a porous hollow-fiber membrane using aromatic polysulfone resin which has a reduced viscosity of 0.36, 0.48, or 0.52.